Voltage boosters may be employed in any number of electronic devices, such as desktop computers, laptops, tablets, data storage devices, as well as consumer electronics, such as cell phones, televisions, gaming devices, etc. In a typical application, a voltage booster may be used to boost a supply voltage that is dropping due, for example, to a battery discharging. In another example, a disk drive may use a voltage booster to boost a backup supply during a power failure so that the current access operation can be completed before parking the heads and shutting down safely.
FIG. 1A shows a prior art voltage quadrupler 2 comprising three charging capacitors C1, C2 and C3, an output capacitor Cout, and a number of switches. FIG. 1B shows control circuitry 4 for implementing a state machine that controls the switches of the voltage quadrupler 2 according to the following sequence:                1. connect C1, C2 and C3 in parallel with Vin to charge VC1=Vin, VC2=Vin, VC3=Vin; and        2. connect Cout in parallel with VC1+VC2+VC3+Vin to charge VCout=4Vin.The above sequence is repeated at a high frequency, transferring energy from C1, C2 and C3 to Cout, thereby generating an output voltage that is quadruple the input voltage.        